1823.] Analyses of Booh, 139 



learned from it, yet it is now treated of as an elementary body, 

 and every part of the work is in unison with this doctrine. 



Another great improvement has been adopted ; in his views 

 of the atomic constitution of bodies, Dr. H.has followed Dr. Prout's 

 opinion with respect to the relative weights of the atoms of hydro- 

 gen and oxygen, viz. as 1 to 8 ; and in doing this, he has also ad- 

 mitted the consequence which results from it, that the weights of 

 all other bodies are multiples of hydrogen by a whole number ; 

 at least his table of the weights of atoms is in agreement with 

 this opinion, nor do these weights differ in many instances, or 

 very materially, from those given by Dr. Thomson. 



There are several parts of the present edition which, as required 

 by the present state of chemistry, have been entirely rewritten ; in- 

 deed one discovery has been made, and has constituted a highly 

 curious and important branch of science since the publication of 

 the former edition ; I allude of course to the subject of electro- 

 magnetism : Dr. Henry has treated of it with brevity ; but he has 

 stated the leading facts of the subject as much in detail as the 

 nature of the case would permit. 



In addition to Electromagnetism, those parts of the work 

 which are either entirely new, or remodelled, are numerous; 

 among others I may enumerate. Corrections for Moisture in 

 Gases, vol. i. p. 25 ; Deutoxide of Hydrogen, p. 262 ; Com- 

 pounds of Carbon and Chlorine, p. 348 ; Hyposulphurous and 

 JHyposulphuric Acids, &c. &c. A new arrangement of the metals 

 has likewise been adopted. 



In the second volume, the additions have also been important, 

 particularly on the subject of the Vegetable Alkalies, Vegetable 

 Analysis, and the Analysis of Mixed Gases. There are several 

 parts of the work which I should like to present to the notice of 

 the reader, and I do not know that I can select a subject which 

 has of late excited more attention, both as a matter of science 

 and of economy, than the nature of the combustible gases produced 

 from the decomposition of coal and oil. With this extract I shall 

 close the notice of a work eminently calculated to inform not 

 only the student, but containing the newer discoveries, which 

 those who have been long acquainted with the science are 

 frequently prevented from acquiring in a more extended form : 



" On the Mixed Combustible Gases from moist Charcoal, Alcohol, 

 Ether, Coal, Oil, Tallow, and Wax,'' 



" The two gases, which have been just described under the 

 names of carburetted and bicarburetted hydrogen, appear to me 

 to be the only compounds of those elements, that have as yet 

 been proved to be distinct and well-characterized species ; 

 though it is extremely probable, as I have shown in the Philos. 

 Trans, for 1820, that another gas exists, which was first observed 

 by Mr. Dalton ; is heavier and more combustible than olefiant 

 gas ; and contains a larger proportion of carbon. It is of mix- 

 tures of two or more of those three gases, with occasionally a 



